In the field of laser safety, laser hazard evaluations are performed to compare laser output parameters against known safety limits to determine the potential for hazardous exposure to optical radiation. Mathematical models have been created to aid in laser hazard evaluations. Because of physiological mechanisms within the eye, multiple laser pulses that occur within a certain time (tmin, known as the thermal confinement duration of tissue) are biologically treated as single laser pulses within these mathematical models.
Historically, most lasers that produced multiple laser pulses did so at regular intervals, so that the number of pulses emitted in a period of time could easily be determined by simply multiplying the pulse repetition rate by the length of exposure. In recent years, however, more and more laser systems have been created that emit multiple laser pulses at irregular intervals in an effort to transfer information from one point to another. An example of this is the Marine Corps/Army MILES laser weapon simulators. These lasers are used for force-on-force training to simulate conventional weapons. Marines and Soldiers wear vests that detect laser energy pulses that are coded by varying the number and timing of pulses. These MILES codes can represent user ID, weapon type, and the kill or near-miss severity of a simulated hit. Since devices like these do not subscribe to the traditional pulsing techniques used previously, determining the number of pulses emitted during an exposure has been very difficult to determine.